How to optimise images for use on the web and elsewhere with a GIMP plugin

GIMP is one of the best free photo editing applications and it has a great range of features. It can be extended even further by adding plugins and here is a free one for optimising images, especially for the web.

Plugins are normally associated with Adobe Photoshop and some of them are quite expensive, but that isn’t the only program that uses them and GIMP has plugins too. GIMP is free and so are many plugins for it.

They add great new features and at http://registry.gimp.org/node/33 is one for optimising images for various purposes, such as for use on the web. You can’t simply put photos on web pages because they are too big and the file size is too large. They must be optimised for size - both the physical dimensions and file size.

Images can be optimised in GIMP using the existing tools like resize and export as a JPEG or PNG, but this plugin makes the process a bit simpler and easier to do. It means that there is less guesswork and fiddling around with menus and options. Everything you need is in the Save window.

As well as adding a useful plugin for GIMP, you will also learn how to extend this photo editing program. All plugins are installed in a similar way.

Optimise photos with GIMP

Start GIMP and load a photo.

Go to the File menu and select Save for Web.

Click the second tab to show the size controls and set them to resize the image. If you are saving for the web, you might want to reduce the size. On this website for example, images are 550 pixels wide.

Switch to the first tab and select the file format to save the image in.

JPEG is good for photos and using the quality slider you can choose between quality and file size.

PNG-24 is a lossless file format, which is pixel perfect, but produces large file sizes, which should be avoided on the web.

PNG-8 and GIF are best for simple artwork with few colours.

The preview window shows exactly how the image will look and this is very useful for JPEG images where you want the file size to be small, but you don’t want to compress it so much that the image quality suffers.

Whenever the controls are adjusted, the image file size is recalculated and can be seen underneath the preview window. This enables you to play around with the quality and size settings to get the best compromise - a fast loading image that still looks good.

This is not the only plugin for GIMP and now that you know how to install them, go and find some more!